#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

int main() {
    char a;
    scanf("%c", &a);
    if ((a >= 'A' && a <= 'Z') || (a >= 'a' && a <= 'z')) {
        printf("YES");
    }
    else
        printf("NO");
    return 0;
}